This may or may not be helpful, but I've seen $1 pocket warmers at the dollar tree and other such stores, especially camping stores, which work wonders. It really only helps with extremities being cold, and they're temporary, but it is something to maybe keep in mind as an option too.
Disposable warmers are pretty indispensable.
In my experience, efficacy may vary by batch/brand, but they're generally a good idea. Some lables advise the product works better in an air-restricted environment; some claim they are air-activated. Generally, I've used them in similar ways.
There are adhesive type and those without. Sometimes the adhesive works well enough to stay even while walking, and it lifts away a bit of the outer surface of the fabric to which it was attached; sometimes the adhesive works less than wishing the warmer would stick. Some are thin (adhesive toe warmers, for instance); some are relatively thick (hand warmers that are basically little packets, for example). Invisible tape works pretty well to keep the poorly adhered warmers in place, and give extra security to those that seem to be sticking well on their own.
For the thin, adhesive style toe warmers, a method that's worked for me is to layer socks and warmers. Usually, only one warmer per foot is enough. The lables say they shouldn't be placed directly on the skin, and I've usually gone along with that. Thin cotton socks (the otherwise relatively useless-seeming 'sport' or 'no-show' socks work very well for this) go on the feet, which should be as close to clean and dry as one can manage. Adhere the toe warmer in a way that's comfortable for you. My toes are fussy, so i have to situate the warmer at a particular angle. Consider focusing on the ends of the toes more than the base near the ball of the feet. When you tape, please make sure to keep the tape lose enough to wiggle the toes. My fussy toes appreciate allowance for wiggling, bending, stretching, and spreading out width-wise. Over that, wear a heavier sock. The socks I've been wearing as an outer layer are some kind of wicking cotton-poly blend, purchased on sale at a regional supermarket for a very low price. I recommend natural plant fibres, synthetics, or a blend of both.
The packet type warmers can also be taped to the toes. In my experience, it is worth paying a bit extra for the thin toe warmers instead, as the packets can become very uncomfortable, even when walking a short distance. They've been known to harden while in use, and that can be even worse than simply the discomfort of the bulkiness.
For sleeping, chilling, whatever isn't walking, you can make a kind of bunting for the feet using a smaller blanket and some sort of article to tie with. This method is not highly recommended if one is going to need to get up and out in a hurry, although I'm sure one could creatively secure their foot blanket bundle in such way that is effective yet easy to become free from, if one is so capable. The downside to that is that if you need to walk outside right away, you don't have a warmer already on your feet, as you would with the adhesive kind. It can be a balance between wearing socks heavy enough (especially if the warmer stops working or losses significant warmth), and wearing socks thin enough (to feel the warmth from the product more directly). The packet might shift if you haven't taped it to your feet or the inside of your foot bundle. (I've woken to my feet rearranging the packet/s, the blanket, even the tie, from the inside -- fussy feet). Obviously, don't tie the bunting too tightly on any part of you. A cheap dollar store polyester 'fashion scarf' will work, as will a robe tie, or anything of similar nature.
The foot warmers were more expensive than the toe warmers, and i don't remember using them very well. Best i currently recall, the toe warmers worked better for me, and the cost difference reinforced the preference. Availability might also have been a factor. They seem a product many people 'stock up' when they're available.
As for hands, I'm incorrigible when it comes to keeping mine warm, and so have little experience using warmers for hands. I think i tried the pocket method once, with poor results, and figured they weren't worth the bother. However, even i will keep my hands under blankets, in my coat, under clothes, etc., at some point, and i encourage everyone to take better care of themself (and each other) than i.
My circulation is pretty healthy; I've usually tended to be ok with cooler digits and extremities; my main concern is usually my toes. Your needs and results may vary. Be safe. Heed warnings and cautions over any of my advice where and when applicable.
My personal recommendation for anyone who is financially able would be to gift these to humans in need -- their utility, in my opinion, can't be understated. Please don't horde them, though -- some of us can only afford / only have space to buy a pair or a few at a time. Anyone working with a 'shelter', or other entity distributing needed goods to the needful people, should, in my opinion, seriously consider distributing these. If you buy stock, buy stock in these. (I'm woefully underqualified to be offering stock tips; I'm simply emphasizing my fondness for, and the usefulness of, toe warmers).
TL/DR: Various disposable warmers are useful. Thin toe warmers are very useful. Inexpensive tape can help keep them in place. Consider wearing between two pair of socks per foot. Be safe. Don't horde.
~peace~
